58 



Stat. 9 1 - Muaras-reef, inner side: East coast of Borneo. Reef. 



Stat. 93. Pulu Sanguisiapo, Tawi-Tawi Islands, Sulu Archipelago. \z m. Lithothamnion-bottom. 



Stat. [81. Ambon. Keef. 



St.it. 215. North point of Kabia Island. Reef. 



St.it. 225. South of Lucipara-group. Reef. 



it. 24S. Rumah Lusi, North-point of Tiur Island. Reef. 



I do not include in this species the form which, according to Hkydricii 1. c, is furnished 

 with cystocarpic conceptacles thus described by him: "Die Cystocarp-Conceptakel sind ausserst 

 selten und bilden auf besonderen Individuen grosse flache und einzelne Erhabenheiten, welche 

 2 1 , mm. im Durchmcsser sind; die Offnung ist 125 — 140 u.. gross". This plant cannot be 

 elassed with the species in question, but probably represents a species of the genus Goniolithou, 

 likelv with emptied conceptacles judging from the large orifice mentioned in the quoted description. 



When the plant grows on an even or fairly even substratum, it forms an even and 

 smooth crust of a hard consistency. PI. XI, fig. 5 represents such a specimen from Funafuti 

 almost coinciding in habit with the type specimen 1. c. fig. 11. Here the plant becomes 

 vigorously developed, partly forming rather thin crusts on branchecl corals, partly, and more 

 frequently, a thick coat on lumpy corals or other hard objects. It also sticks to consolidated 

 rock, forming platform or hurricane beach, and attaining a thickness of up to about 1,5 cm., 

 frequently, however, less. The figured specimen shows young and circular crusts developed 

 upon the primary one, and in the upper corner it is confluent with a piece of a coral. 



In the Siboga collection occur no specimens so regularly developed as the above 

 mentioned one, but there are a few rather vigorous ones here too (PI. XI, fig. 9 — 10). The 

 shape of the crust depends, however, on that of the substratum, as in a number of other and 

 particularly crustlike species, and sometimes the plant even conveys an impression of developing 

 excrescences. Cp. pi. XI, fig. 7, which represents a specimen covering a bucky. In this collection 

 the species in most cases forms more or less irregular and but little expanded crusts in company 

 with other calcareous algae, Bryozoa, small corals and other animals, attached to hard objects 

 of different shape and size, mostly, however, dead corals. Sometimes it forms small cap-shaped 

 crusts on excrescences of corals, together with other algae and sponges, occasionally even 

 recalling a young Lithophyllum Okamurai (PI. XI, fig. 8). The specimen here figured shows 

 a looser consistency than usual in this species, probably owing to the substratum. 



As regards structure, the perithallic layer of the plant is thus described by Hevdricii 1. c. : 

 "Die übrige grosse Thallussubstanz wird von keinen bemerkenswerten Schichtungen durchzogen, 

 weshalb man von irgend einer bestimmten Aufeinanderfolge derselben nicht reden kann ; ab und 

 zu erscheinen grössere oder kleinere zerstreute Zeilen, die aber dem Inneren ein noch unregel- 

 massigeres, aber sehr characteristisches Geprage verleihen. Die grosseren Zeilen sind etwa 8 y.., 

 die kleineren 5 y.. im Durchmesser". — From a specimen distributed by Hevdrich himself and 

 trom vertical sections of other typical specimens I have found the perithallium to be composed 

 of cells which are partly squarish or somewhat rounded, 6 — 9 u. in diameter, partly slightly 

 horizontally or, more frequently, vertically elongated and in the latter case up to about 18 a. 

 long. The cells are now rather thick-walled, now thin-walled. Besides, in this layer of tissue 

 are to be found short horizontal rows of larger cells, partly occurring in great number, partly 



